Madhavi Devi was an elderly lady & one of the most confidential Devotee of Shri Chaitanya Mahaprabhu. Her elder brother was Sikhi Mahiti and brother Murari Mahiti. Along with her Sikhi Mahiti and Murari Mahiti, she constantly associated with Chaitanya Mahaprabhu while He resided in Jagannatha Puri.
In the Antya-lila of Chaitanya-charitamrta there is a description of Madhavi Devi.
mahitira bhagini sei, nama—madhavi-devi
vrddha tapasvini ara parama vaisnavi
(C.C.3.2.104)
Sikhi Mahiti’s sister was named Madhavi Devi. She was an elderly lady who always performed austerities. She was very advanced in devotional service.
Chaitanya Mahaprabhu had three and a half very confidential Devotees. The three are mentioned below.
svarupa gosañi, ara raya ramananda
sikhi-mahiti—tina, tanra bhagini—ardha-jana
(C.C.3.2.106)
The three were Svarupa Damodara Goswami, Ramananda Raya and Sikhi Mahiti, and the half a person was Sikhi Mahiti’s sister, Madhavi Devi.
Shrila Prabhupad writes in purport: In the Gaura-ganoddesa-dipika (189) it is said that Sikhi Mahiti was formerly an assistant of Shrimati Radharani named Ragalekha. His sister Madhavi was also an assistant of Shrimati Radharani and was named Kalakeli. Sikhi Mahiti, Madhavi and their brother Murari Mahiti were all unalloyed Devotees of Shri Chaitanya Mahaprabhu. He and his brother and sister always engaged in rendering service to the Lord.
prabhu lekha kare yare—radhikara ‘gana’
jagatera madhye ‘patra’—sade tina jana
(C.C.3.2.105)
Shri Chaitanya Mahaprabhu accepted her as having formerly been an associate of Shrimati Radharani. In the entire world, three and a half people were His intimate Devotees.